The H-alpha 12nm CCD Filter - SC Rear Cell by Astronomik:
This Astronomik H-alpha 12nm filter is a narrow band emission line filter designed for astrophotography. It allows for the H-alpha light of emission nebulae to pass through while blocking almost the entire remainder of the spectrum where the CCD is sensitive.
This filter's full width at half-maximum (FWHM) of 12nm was developed for use with typical CCD cameras and permits the use of very fast optics. It would be prudent to note that this filter has a transmission of up to 99-percent. An additional advantage of this 12nm filter is the availability of guiding stars for cameras with an integrated SBIG autoguider. For those using a very strong filter such as Astronomik's 6nm H-alpha, you most likely won't be able to locate a usable guide star.
This filter's application range expands from 1:2.8 to 1:15. Astronomik filters will present problems with transmission losses and chromatic distortions only when extremely bright aperture ratios of 1:2 or more are brought into play.
The 12nm version of the Astronomik H-alpha CCD filter enhances the contrast between objects, in this instance between the H-alpha emission line and the background in the same fashion as the 6nm model. It thoroughly covers up emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. When using OIII and SII CCD filters you can attain three-color images of emission line objects such as gas nebulae from heavily light-polluted locales. To accomplish this, you would need to take an image in three separate wavelengths, choose each as a color-channel in Photoshop, and combine them into one color image.
Do not use this filter for solar viewing. If you intend to construct color images from emission line data, Astronomik's CLS-CCD filter is an excellent choice for the Luminance channel.
Astronomik H-alpha 12nm CCD Filter - SC Rear Cell Features:
- Transmission of above 97-percent with the H-alpha line (656nm)
- Total blocking of all disturbing wavelengths in the infrared
- Parfocal with all other Astronomik filters
- 1mm glass thickness
- Entirely resistant to high humidity, scratches, and aging impact
- Diffraction limited, the filter will not lessen the optical performance of your telescope!
- Astronomik filters are presented in a high-quality, durable, filter box
OPT Product Number: AK-HA12-SCT